Adding ddl audit trigger

Trying to get some DDL auditing in a development environment by adding triggers to pg_proc, pg_class,pg_type,pg_trigger and getting the following error:

ERROR: permission denied: "pg_proc" is a system catalog
SQL state: 42501

Is there any way to achieve DDL auditing in Postgres and trace any new/dropped/changed object into a table?
All I need is to at least be able and save a userid(current_user), timestamp, action, and the name of the object and this could be done easily by adding triggers to these pg catalogs.

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